Document folders allow you to share documents and assets with your team - everything in one easy-to-find place. The folders have to be set up by someone with Admin level permissions.
Setting up folders
Firstly set up your Document folder from the Team folder section of the Admin panel
It's a good idea to set up your Document folder first in whatever cloud drive you are planning to use so that's Dropbox, Google Drive or One Drive. Then add the folder to your account. You can only add one Document folder.
So I've added my Document folder, now I need to go into the Assets tab to include Logos, Images and any other assets I may require.
Click on one of the Icons (Logos, Images, Other) and then add a folder from one of the cloud drive (Dropbox, Google Drive, One Drive) options - it doesn't have to be the same cloud drive as the document folder that your created in the first step and you can add as many folders as you like.
So here I've linked to a folder which contains my images, now I can go ahead and link a folder to the other two options if I need to as well...
Now when I launch the Document Editor and open a document I can add documents and items from my Team Assets from the Add + menu.